Chernobyl Health Effects Still Not Known

Shoes and a gas mask for children are left in a kindergarten in Ukraine's ghost town of Pripyat - near Chernobyl

"It's only a matter of time," she said as she waited for a thyroid test at a mobile Red Cross clinic in her village of Bystrichy, 240 km west of Chernobyl.

The tests came back clean, but that's little reassurance to this 54-year-old or to millions of others who live in parts of Ukraine, Belarus and Russia that were heavily irradiated when the nuclear reactor exploded 20 years ago, spewing radioactive clouds over Ukraine and much of Europe for 10 days.

The April 26, 1986, disaster forced the evacuation of large swaths of some of the Soviet Union's best farmland and forests. The radiation spread far enough to be detected in reindeer meat in Norway and rainfall in the U.S. Pacific Northwest.

It shocked most European countries into a generation-long freeze on building nuclear plants. And the effect on the health of the people exposed to its invisible poisons? That is the most heatedly debated legacy of Chernobyl.

"There is so much that we still don't know," said Dr. Volodymyr Sert, head of a team of Red Cross doctors who canvass Ukraine's rural Zhytomyr region in search of thyroid abnormalities — one of the few health problems that all scientists agree is linked to Chernobyl's fallout.